(30*x-560)
= 80
8
30*x-560=640
30х=640+560
30х=1200
х=1200/30
х=40
Проверка:
(30*40-560)
640
= 80 80=80
30x-560=80*8
30x-560=640
30x=640+560
30x=1200
x=1200:30
x=40
(30*40-560):8=(1200-560):8=640:8=80
(30*x-560)
= 80
8
30*x-560=640
30х=640+560
30х=1200
х=1200/30
х=40
Проверка:
(30*40-560)
= 80
8
640
= 80 80=80
8